HOW TO DO AN ADVANCED SEARCH.

Mon Jul 08, 2013 3:56 pm by Admin


For the benefit of 944Hybrids users there are two search functions available for you to use.
The purpose of this sticky is to explain the "Advanced Search" function because it is much more powerful and is the best choice when researching information.

When you log on to the site a list of options is shown in a line at the top of the page. One option is labelled "Search", use this option (NOT the search box lower down on the right).

After you click on the upper search option, a drop down box appears. At the bottom of this box is a radio button marked "Advanced …

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Tire Size (width)

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Tire Size (width)

Post  Lemming on Fri Dec 05, 2014 3:32 pm

Ok, let's not discuss staggered tire sizes, I have been running 275s on all corners and plan to continue to run with one width for both ends of the car.  I do however want to discuss width.  Currently my 275s can go 90 minutes without overheating, and in fact I usually run my best laps near the end of an enduro.  On the other hand, it takes forever for me to get heat into my tires and this kills me at the beginning of all races.  I'm considering trying 255/40-17s for short sprints (30 min or less) so that I can get up to speed faster.  Has anyone run 255s or even 245s.  Car is around 2700-2750 lbs (with me and fuel) and is pushing less than 350 rwhp.  

I know that I can run softer compounds in 275 to get the same effect (quick heat up time), but these tires tend to heat cycle out much faster and are a budget killer.
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Re: Tire Size (width)

Post  jpkinerk on Fri Dec 05, 2014 3:46 pm

I've not been on the track yet with them, but I'm running 255/40-17 all the way around with Dunlop Direzza DZ102s. I can't comment on their thermal characteristics, but I do know with a mere 317 rwhp, my car will borderline blow the tires off shifting into 3rd at WOT. Some good heat in the tire may change that. In the twisties though they still inspire confidence, even when pretty cold, so nothing negative stood out in that respect.
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Re: Tire Size (width)

Post  Rich L. on Fri Dec 05, 2014 8:58 pm

I run 255/40 NT-01 tires on 17x9 Cup II wheels. Square. I feel like they come up to temp nice and quickly but I'm not doing race starts. Wear is even if I rotate regularly and I'm very happy with tire life. But I do find that my mid-corner speed is way slower than the 911s I run with, most of whom are on wider Hoosiers.

Hope that helps.
Rich
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Re: Tire Size (width)

Post  racertomtom on Sat Dec 06, 2014 12:08 am

Interesting.  My first thought is your car must be VERY well set up for that to even be possible. My second thought is your tires probably are slightly too hard for your current tracks, weight and balance. My third thought is, isn’t that how enduros are? You either save tires and finish strong or wear them out and finish slow?

While going with a narrower tire would heat up the tire quicker, the question is, will a hot narrow tire hook up as well as a warm wide tire with your set up? I think chassis set up is more critical on a narrow tire and you might wind up chasing your tail for a while with set up. In other words, your set up may not like a narrow tire. It might be surprising what a half inch of tire can do. IMO you could go with a slightly softer compound with your current setup without cycling out being an issue as long as you don’t go so soft that the tires overheat in the endurance runs.  I always thought setting up a car was as much luck as skill. Good Luck!

In my drag racing days, I ran stupid soft compounds compared to a road race tire. I would heat cycle the tires a couple hundred times over 30+ weekends without issue. It wasn’t until the tires came out of heated winter storage that they were crap. Not over heating them and racing them seems to be the key. Saving softer compounds just for sprints might do them in.

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Re: Tire Size (width)

Post  Lemming on Sat Dec 06, 2014 9:39 am

I'm lucky to get 4 heat cycles out of A6s before they drop off the cliff, the A7s may be better, but are not available in my size. I can get away with running A6's for sprint races when temps are below 70, and for time trials and qualifying at any temp, but they kill my race budget. R6s are good for 6-8 heat cycles, and Z214s (C51) for 8-12 before they become practice/DE tires. I've not run the C71s, but right now you cannot find Hankooks anywhere in 275. Tirerack suggested that it would be 2-4 months before they had more Kooks in 17s.

I'm not convinced that the tread width would be 0.6" difference between the 275/255 tires. Why, I'm running 17x9 wheels and 275s are measured on 9.5 wheels, so I'm not getting the full width or even optimal setup. On the other hand, 9" wide wheels are optimal for 255's.

Setup could be an issue, so I might wait till I have a few non-race weekends to play with the setup. I have a couple of racing friends running E46 M3s that have similar power to my car but weigh more and they are successfully running 255s. The other advantage to 255/40-17s is a decrease in ride height.
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Re: Tire Size (width)

Post  racertomtom on Sat Dec 06, 2014 10:22 am

The optimum compound not being available in your size makes the 255s more attractive. Your lighter weight should perform better than your friend’s heavier cars and there is a lot to be said about optimal rim width. Smaller diameter also means lower gear ratio and also a smaller contact patch, but I can’t imagine it being noticeable. It does sound like 255s are your best option to me. Your car may even handle better than it does now, who knows.

Edit: People want to believe that wider and stiffer is always better, but that is simply not the case.

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Re: Tire Size (width)

Post  Rich L. on Sat Dec 06, 2014 12:33 pm

Agreed that 275s on 9" wheels isn't optimal. Here are some pictures of worn 275 NT-01s on 9" versus 10" wheels. Lots of variables here but also some interesting text quoting experts. (grain of salt...)

http://www.sn95forums.com/showthread.php?44442-ReplicaR-s-daily-driven-road-race-Mustang-build&s=2f797add3d6cb5ac4159ad1f745304a2&p=1204326&viewfull=1#post1204326

I have ideas of doing widebody fenders and 18x10" wheels to run 295s. But just going to a stickier 255s with my current wheels might be a smarter way to go.

Rich
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Re: Tire Size (width)

Post  docwyte on Sat Dec 06, 2014 7:20 pm

I run the exact same setup, same Cup 2 17x9 wheels with 275-40-17 tires. My car weighs a bit more than yours and makes more power/torque. The big factor is it's hot as Hades most the time I'm on track, so I don't seem to have issues with getting heat into the tires.

I would be curious to see a measurement of a 255 on these wheels vs the 275, if in reality the width is pretty much the same I could save some points by going to the smaller tire.

I wasn't able to get out very much the last two seasons, so I'm still on a very old set of RA1's. Once I cord them I plan on trying the new Toyo RR's.

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Re: Tire Size (width)

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